Have you tried using the wiki? If you read it carefully it can tell you quite a it.
Horrible things have happened.
After my war dragon torched the trap hallway and half the goblin siege outside, sending the rest running home like my marksdwarves never could, I decided to use dragons in the defences. I made 1x tunnels through a walled-off area on either side of the dodge-pit bridge with fortifications in the walls themselves, so the dragons pastured in those tunnels could torch sieges from relative safety (until they run out through the open door on the interior of the bridge causeway), with raising drawbridges along the exterior fortifications to prevent the dragons from engaging some hostile groups until I desired them to. Unfortunately, one of the bridges refused to be finished claiming there was an item blocking site despite absolutely no items in that area, that war dragon mysteriously died (I honestly couldn't figure out what happened, it torched some poor beekeeper/other useless farmer, and I only have three other dragons fit for use. So, the defenses weren't ready for the sieges next season, and many of the weapon traps in the dodge-pit causeway had wooden weapons and thus were roasted by the dragon and didn't get repaired in time.
Next season, another siege. The traps didn't do squat, as is their custom of letting the leader dodge in and his entire squad stops in their tracks just outside until my rangers, who don't have enough amunition, shoot them a couple times and they too run in one-at-a-time. (I need to come up with a design that entirely circumvents this issue.)
It went a little differently this season; the rangers got up there after the leaders dodged in, and they took potshots at the goblins. A mass of them charged in all at once, despite none of them even being shot, and even though they all dodged in they agro'd my melee troops who were stationed at the back of the bridge since many of the traps were missing. About 4-5 of my soldiers charged outside and engaged the goblins around the gates, also discovering one cyclops and one minotaur ambush. I restationed the squads and they all charged outside and engaged, but unfortunately we had two fatalities, one being a legendary shield user who got stabbed in the heart. One recruit was horribly injured and as far as I know is still in the hospital. I also discharged two other soldiers from that same squad that had taken casualties because they were married, and married dwarves don't belong in the militia. Their replacements aren't that great, but at least I have a couple veterans to place in the guards whenever I get around to building a prison...
A child was also stolen from us by a snatcher, and another minotaur snatcher became enraged and killed a fisherdwarf before he could be put down.
And now someone's pet mushroom man is trying to beat a cyclops child snatcher to death... I feel bad for the guy. He escaped, but I certainly wouldn't be stupid enough to return after taking such a beating from the least threatening creature in my enemy's stronghold.
This season is going smooth as far as repairing the defences, but with all this warfare going on I've never been able to set up a few of the industries and civil projects I usually do, and metalcrafting is suffering from a lack of material, especially materials suitable for bolts for the rangers. The fort's a mess.
Turns out 126 dwarves just isn't enough for all the work I want to get done...